How to develop nuclear fuel: for example, one news
The Breakthrough project is known to many as an attempt to break the deadlock into which fast reactors and a closed nuclear cycle entered. On the example of the latest news on testing experienced fuel assemblies in this project, I would like to show how the developers of nuclear fuel work, or rather, part of their work.
Yesterday there was news: Chief Technologist of the Proryv project, Vladimir Troyanov, reported on the results of post-reactor studies of the first combined experimental fuel assembly (KETVS-1) with mixed nitride fuel.
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Project image of a pilot center with a BREST-300-OD reactor. MP - module for SNF reprocessing, MFR - module for fabrication / refraction of a new fuel with a capacity of 14.7 tons of fuel (per SNUP) per year.
From the point of view of scientists, the first post-reactor studies conducted at the State Scientific Center - Research Institute of Atomic Reactors (GNTs-NIIAR) gave phenomenal results. “There were no violations in the integrity of the fuel column, the low deformation of the membranes was very pleased,” Vladimir Troyanov reported. experimental data shows that the condition of fuel elements with nitride fuel is satisfactory and their resource is far from exhausted.
Three years ago, SSC-NIIAR manufactured a combined experimental fuel assembly, which included four experimental fuel rods with nitride fuel produced by VNIINM them. Academician A.A. Bochvar ”. The assembly was loaded into the BN-600 reactor at the Beloyarsk NPP. After she completed the specified resource, she was removed from the reactor and placed in the in-core storage for six months to reduce heat generation to an acceptable level. Then this experimental fuel assembly was returned to RIAR for post-reactor studies. The first research cycle was completed at the end of October 2015. In general, the program of all post-reactor studies of the first experimental fuel assembly with mixed nitride fuel is calculated until mid-2016. It provides for various, including destructive research.
At present, six experimental fuel assembly with mixed nitride fuel fully manufactured at JSC SCC are being tested in the BN-600 reactor. In addition, SCC specialists took part in the manufacture of four combined experimental assemblies.
The obtained research results will form the basis for licensing the substantiation of the performance of nitride fuel in fast reactors. The results of the work will be used in the implementation of the project for the creation of a pilot-demonstration energy complex as part of the BREST-OD-300 reactor installation and on-site modules for the production of dense fuel and the processing of irradiated dense fuel at the site of SCC.
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What is it about here? First we need to remind you that one of the keywords here is “nitride”: instead of the standard uranium dioxide UO 2, it is planned to use UN uranium nitride and PuN plutonium here. Oxides are known far and wide, having accumulated millions of fuel assemblies in the reactor. Nitrides are much less well known, and from all sides - how to make nitride powder, a fuel pellet, how it behaves in the reactor, how it interacts with structural materials and heat carrier, etc. Why are they used in Breakthrough? Uranium-plutonium nitrides have a higher density, which means a higher specific content of fissile materials in the core, less loss of neutrons, and a higher reproduction rate of plutonium. With the help of nitrides Kv> 1 can be obtained for the zone without reproducing screens, which significantly simplifies operation. Evil tongues say besides that nitrides are chosen because the oxides float in the lead coolant, that there is no ice in the destruction of a fuel rod :) So, a breakthrough project is planned for extensive studies of the behavior of nitride fuel, including by studying the physicochemical characteristics of irradiated fuel .
What is planned to make a lot of experimental fuel assemblies, some of them will be needed to determine the behavior of the fuel "in general", some - for differences in the behavior of fuel in future fuel assemblies of fast PRORIV reactors from "in general".
The top line is the fuel assembly that was successfully irradiated in the reactor up to 6% of burnout, then it fell down and passed the post-reactor tests (DRE). It is followed by 4 more quite experienced KETVSs, and then even more close to the workers of the TVS BREST-300 and BN-1200 on the nitride fuel ETVS-3 ... 15
8% TA means that 8 percent of plutonium in a fuel assembly will decay (with approximately equal amounts of fresh plutonium being accumulated from U238). This is quite a lot - twice as much as in modern pressurized water reactors. At the same time, this is only half of the initial loading of plutonium in fuel assemblies (17% of heavy metal, the rest is U238) - and this is one of the most important reasons why fast reactors are not viable without radiochemical processing: fuel consumption is too low.
As we can see, burnout on the ETVS will be accumulated gradually, from the fuel assembly to the fuel assembly. Such levels of dose-related damage are not easily achieved: the tablets swell, the embrittlement material swells and the shell material swells, gaseous fission products accumulate in the fuel element. How are these effects on fuel being investigated, what happens during mysterious PRI?
FA after irradiation is very, very radioactive. Therefore, all studies are conducted remotely, in hot cells. For a start, the fuel assembly is disassembled or sawn, so that it would be possible to reach individual fuel rods. After this, a non-destructive and destructive research of fuel rods begins.
We look, whether there is no deformation and damage.
Make an X-ray of irradiated fuel.
Using a gamma spectrometer, we determine the distribution of plutonium fission products along a fuel element. Why does he have this form? Because the intensity of a nuclear reaction is uneven along a fuel element:
Now we need to know the next important parameter - how much nuclear fuel is subject to swelling and cracking. We pierce the fuel element and measure the gas composition inside:
Well, only 5% of the gaseous fission products went into the volume of the fuel element, the rest is locked in the fuel matrix. Cut TVEL, take pictures and measure tablet form change:
The fuel is cracked ... but how much is it swollen? Measure geometry
We see that the change in volume is pretty decent. Such a swelling will not give a burnout higher than 4.5-5%. However, it has two natures - the appearance of gas pores inside the fuel and the swelling of the crystal lattice due to radiation damage. The first is less dangerous than the second. After measuring the volume of the samples in the liquid, we see
The main effect introduces porosity, i.e. gaseous products. Well, perhaps technological changes at the stage of preparation of the fuel powder, pressing and sintering the tablets will give the best results.
Something like this, and sometimes even more cunning and complex methods, investigate all the new fuel, comparing the results with the simulation. The complexity, duration, high cost of such research largely determines the duration and high cost of any nuclear power development. Therefore, it is very pleasing when you see that similar work in the Breakthrough project is carried out in accordance with the schedule and the results please the creators.
Yesterday there was news: Chief Technologist of the Proryv project, Vladimir Troyanov, reported on the results of post-reactor studies of the first combined experimental fuel assembly (KETVS-1) with mixed nitride fuel.
')
Project image of a pilot center with a BREST-300-OD reactor. MP - module for SNF reprocessing, MFR - module for fabrication / refraction of a new fuel with a capacity of 14.7 tons of fuel (per SNUP) per year.
From the point of view of scientists, the first post-reactor studies conducted at the State Scientific Center - Research Institute of Atomic Reactors (GNTs-NIIAR) gave phenomenal results. “There were no violations in the integrity of the fuel column, the low deformation of the membranes was very pleased,” Vladimir Troyanov reported. experimental data shows that the condition of fuel elements with nitride fuel is satisfactory and their resource is far from exhausted.
Three years ago, SSC-NIIAR manufactured a combined experimental fuel assembly, which included four experimental fuel rods with nitride fuel produced by VNIINM them. Academician A.A. Bochvar ”. The assembly was loaded into the BN-600 reactor at the Beloyarsk NPP. After she completed the specified resource, she was removed from the reactor and placed in the in-core storage for six months to reduce heat generation to an acceptable level. Then this experimental fuel assembly was returned to RIAR for post-reactor studies. The first research cycle was completed at the end of October 2015. In general, the program of all post-reactor studies of the first experimental fuel assembly with mixed nitride fuel is calculated until mid-2016. It provides for various, including destructive research.
At present, six experimental fuel assembly with mixed nitride fuel fully manufactured at JSC SCC are being tested in the BN-600 reactor. In addition, SCC specialists took part in the manufacture of four combined experimental assemblies.
The obtained research results will form the basis for licensing the substantiation of the performance of nitride fuel in fast reactors. The results of the work will be used in the implementation of the project for the creation of a pilot-demonstration energy complex as part of the BREST-OD-300 reactor installation and on-site modules for the production of dense fuel and the processing of irradiated dense fuel at the site of SCC.
================================================= ===============================================
What is it about here? First we need to remind you that one of the keywords here is “nitride”: instead of the standard uranium dioxide UO 2, it is planned to use UN uranium nitride and PuN plutonium here. Oxides are known far and wide, having accumulated millions of fuel assemblies in the reactor. Nitrides are much less well known, and from all sides - how to make nitride powder, a fuel pellet, how it behaves in the reactor, how it interacts with structural materials and heat carrier, etc. Why are they used in Breakthrough? Uranium-plutonium nitrides have a higher density, which means a higher specific content of fissile materials in the core, less loss of neutrons, and a higher reproduction rate of plutonium. With the help of nitrides Kv> 1 can be obtained for the zone without reproducing screens, which significantly simplifies operation. Evil tongues say besides that nitrides are chosen because the oxides float in the lead coolant, that there is no ice in the destruction of a fuel rod :) So, a breakthrough project is planned for extensive studies of the behavior of nitride fuel, including by studying the physicochemical characteristics of irradiated fuel .
What is planned to make a lot of experimental fuel assemblies, some of them will be needed to determine the behavior of the fuel "in general", some - for differences in the behavior of fuel in future fuel assemblies of fast PRORIV reactors from "in general".
The top line is the fuel assembly that was successfully irradiated in the reactor up to 6% of burnout, then it fell down and passed the post-reactor tests (DRE). It is followed by 4 more quite experienced KETVSs, and then even more close to the workers of the TVS BREST-300 and BN-1200 on the nitride fuel ETVS-3 ... 15
8% TA means that 8 percent of plutonium in a fuel assembly will decay (with approximately equal amounts of fresh plutonium being accumulated from U238). This is quite a lot - twice as much as in modern pressurized water reactors. At the same time, this is only half of the initial loading of plutonium in fuel assemblies (17% of heavy metal, the rest is U238) - and this is one of the most important reasons why fast reactors are not viable without radiochemical processing: fuel consumption is too low.
As we can see, burnout on the ETVS will be accumulated gradually, from the fuel assembly to the fuel assembly. Such levels of dose-related damage are not easily achieved: the tablets swell, the embrittlement material swells and the shell material swells, gaseous fission products accumulate in the fuel element. How are these effects on fuel being investigated, what happens during mysterious PRI?
FA after irradiation is very, very radioactive. Therefore, all studies are conducted remotely, in hot cells. For a start, the fuel assembly is disassembled or sawn, so that it would be possible to reach individual fuel rods. After this, a non-destructive and destructive research of fuel rods begins.
We look, whether there is no deformation and damage.
Make an X-ray of irradiated fuel.
Using a gamma spectrometer, we determine the distribution of plutonium fission products along a fuel element. Why does he have this form? Because the intensity of a nuclear reaction is uneven along a fuel element:
Now we need to know the next important parameter - how much nuclear fuel is subject to swelling and cracking. We pierce the fuel element and measure the gas composition inside:
Well, only 5% of the gaseous fission products went into the volume of the fuel element, the rest is locked in the fuel matrix. Cut TVEL, take pictures and measure tablet form change:
The fuel is cracked ... but how much is it swollen? Measure geometry
We see that the change in volume is pretty decent. Such a swelling will not give a burnout higher than 4.5-5%. However, it has two natures - the appearance of gas pores inside the fuel and the swelling of the crystal lattice due to radiation damage. The first is less dangerous than the second. After measuring the volume of the samples in the liquid, we see
The main effect introduces porosity, i.e. gaseous products. Well, perhaps technological changes at the stage of preparation of the fuel powder, pressing and sintering the tablets will give the best results.
Something like this, and sometimes even more cunning and complex methods, investigate all the new fuel, comparing the results with the simulation. The complexity, duration, high cost of such research largely determines the duration and high cost of any nuclear power development. Therefore, it is very pleasing when you see that similar work in the Breakthrough project is carried out in accordance with the schedule and the results please the creators.
Source: https://habr.com/ru/post/367087/
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